In the present market, a disc brake has been firstly selected as a braking system of a bicycle. The single moving mechanical disc brake, the dual moving mechanical disc brake and the oil pressure disc brake are prevalently used in the current market. In the single moving disc brake, the disc may be pushed toward one side to be deformed due to one-sided movement of the brake pads, and is not easy to be adjusted when mounted. Moreover, the drawing arm for the brake cable may be seen in the single moving mechanical disc brake without satisfactory aesthetics. Similarly, the brake cable and the drawing arm may be also seen in the dual moving mechanical disc brake in the current market, which leads to the problem of unsatisfactory aesthetics equally. In addition, abuses including liability to oil leakage, thermal expansion, difficult adjustment, troublesome maintenance and etc., are presented in the oil pressure disc brake with higher cost.